The kabbalistic calendar is lunar, based on the cycle of the moon, while the Gregorian calendar is based on the cycle of the sun. Seven times within a 19 year cycle, we have a leap year in the kabbalistic calendar, and this is one of those years. While the Gregorian calendar adds a day for leap years, we add a month before Adar, or Pisces; we call it Adar I, and the month after it, Adar II.
Every month has a different angel; an angel, without going into detail, is simply a conduit for a specific type of Light, blessing, or energy. Therefore, the kabbalists teach that every month has a different angel that is the conduit for the Light and blessings of that month. The angel that controls and is the conduit for the Light and blessings for the month of Adar is called Avarachiel, which literally means "I will bless with the Light of the Creator." It says that this angel has twenty-five angels, or twenty-five levels of Light, underneath him who pour that Light and energy into this month.
As we begin this new month of Adar and awaken the consciousness we want to have for it, we ask that Avarachiel come to us and begin shining down that Light and those blessings in this month for us. But why is Avarachiel, the angel of blessings, the angel that controls and showers down Light and energy in the month of Adar?
Because Adar is the month of blessings, and therefore Avarachiel, the angel of blessings, controls it. During the month of Adar we can draw the energy and Light of sustained blessings… and it has to do with the work of consciousness - to be able to consistently shift our consciousness and work on divorcing ourselves from our ego thoughts. If we push to work towards that consciousness, we are able to receive sustained blessings in this month. It is a wonderful gift that is awakened at the beginning of Adar that we can carry into the whole month.